On Mon, 2007-10-22 at 18:28 +0200, Aurelien Jarno wrote: > On Mon, Oct 22, 2007 at 09:36:07AM +0200, J. Mayer wrote: > > Hi all, > > > > I've been investigating more about PreP kernel boot using Qemu and I > > achieved to boot 2.4.35, 2.6.12 and 2.6.22 kernels using Qemu CVS and > > unmodified OHW. > > The issues I found in the kernel are: > > - the OpenFirmware video console driver is broken in recent 2.4 kernels > > and have been removed from recent 2.6 kernel > > - I then decided to use the vga16fb console driver but needed to do some > > patches in order to make it compile properly > > - the CMOS RTC driver is not available for PPC architecture in 2.6 > > kernels and need some patches in order to be usable > > - I discovered that the mkprep utility is bugged in 2.4.35 and 2.6.12 > > kernels. The bugs are visible only when cross-compiling from a > > little-endian and/or 64 bits host. > > - I got issues (ie process freezing) when using the 2.6.22 kernel with > > HZ > 100. It seems to run properly when the system timer is set to 100 > > Hz but this needs more tests for confirmation. > > - I got the 2.6.22 kernel crashing (ie kernel Oops in workqueue code) > > when it has no RTC available. There is no problem when the RTC is > > present. This is likely to be a kernel bug: when no RTC is available, it > > cannot calibrate its timers properly and the kernel timer seems to run > > very fast. Forcing (with hacks...) the timer to run at nearly real-time > > seems to prevent the bug to happen. > > > > I then generated some kernels that allow me to boot and use those 3 > > kernels. > > Here are 3 tarballs with: > > - a patch to be applied to the vanilla kernel sources to fix the > > mentionned bugs > > - the .config file I used to build the kernel > > - the zImage.prep image > > <http://perso.magic.fr/l_indien/qemu-ppc/linux-tests/linux-2.4.35-prep.tar.bz2> > > <http://perso.magic.fr/l_indien/qemu-ppc/linux-tests/linux-2.6.12-prep.tar.bz2> > > <http://perso.magic.fr/l_indien/qemu-ppc/linux-tests/linux-2.6.22-prep.tar.bz2> > > > > I then run Qemu with the following command line template: > > ./ppc-softmmu/qemu-system-ppc -serial stdio -net nic,model=ne2k_isa -net > > tap -net nic,model=ne2k_pci -net tap -net nic,model=rtl8139 -net tap > > -cpu 604 -M prep -L pc-bios/ -hda <my_first_disk> -cdrom <my_cdrom> > > -kernel > > <src_base>/linux-<kversion>.patched/arch/ppc/boot/images/zImage.prep > > > > Hope this helps. > > > > Yes, this help a lot, thanks! With your config file, I have been able to > build and boot a 2.6.22 kernel. I have used a Debian sid chroot. > > Here are a few remarks: > - The NE2000 card doesn't work for the same reason as with the powerpc > architecture. The kernel patch below fixes the problem. I will send it > later along with the ppc patch.
There's something else strange with the PCI ethernet devices: they got no IRQ assigned (as if the BIOS does not configure them properly). And the RTL8139 never has a mac address, never detects the PHY link, then there may be endianness issues in the emulation (I did not check at all). > - The "floating point" problem I reported during the week-end does not > exists, probably because of the switch from powerpc to ppc. I still > don't know if it is a kernel problem or a QEMU problem (or both). There may be issues with the floating point emulation, especially if some kernel or programs relies on the FPSCR (floating-point status) register which is never updated in Qemu. > - PCI is broken. PCI IDs are reported in the wrong endianness: > 00:00.0 Non-VGA unclassified device: Unknown device 0148:5710 (rev 06) > 00:01.0 Non-VGA unclassified device: Santa Cruz Operation Unknown device > 3412 (rev 03) This does not happen with 2.4 kernels. Using the 2.4.35 image, all PCI descriptors are OK and the drivers properly recognize the devices. What I suspect is that 2.6 kernels tweak the chipset to make it handle the endian-reverse accesses. [...] -- J. Mayer <[EMAIL PROTECTED]> Never organized